The invention relates to loudspeakers and, more particularly to bending wave panel-form loudspeakers, e.g. resonant panel loudspeakers of the general kind described in International patent application WO97/09842, which describes technology that has come to be known as distributed mode or DM technology. In particular the present invention relates to bending wave panel-form loudspeakers integrated into or attached to vehicle windscreen or windshield accessories, e.g. as in an automobile sun visor or rear view mirror.
A sun visor for an automobile or other vehicle is generally a hinged flap or panel which at rest is retracted against the roof of the vehicle but which may be moved on a hinge or other mechanism into a position of use to obscure part of the windscreen or windshield to shield the eyes of vehicle occupants, and particularly the vehicle driver""s eyes, from the sun.
It is known to suggest the incorporation of slim-form loudspeakers in an automobile sun visor. Such an arrangement has certain disadvantages, amongst which is the fact that conventional pistonic loudspeakers are directional and thus when incorporated in a sun visor may only be optimally positioned when the visor is in a certain position. It is indeed likely that the optimal acoustic positioning of the loudspeaker in the sun visor will occur only when the visor is in use, whereas for most of the time the visor is likely to be in its retracted position. In addition conventional loudspeakers, even of slim form, are relatively bulky and heavy and may present an unacceptable injury risk positioned close to the head of the vehicle occupants.
U.S. Pat. No. 4,362,907 of Polacsek describes a combination automobile sun visor and radio and speaker assembly, in which the speaker is a thin, bi-directional device.
According to the invention, there is provided a vehicle windscreen accessory comprising a body member, an adjustable support structure for the body member whereby the position of the body member can be adjusted, the body member comprising a mirror member and a loudspeaker having a bending wave panel-form acoustic member, the mirror member and panel-form member being integral.
From one aspect the invention is a vehicle sun visor comprising a sun shield member and an adjustable support structure for the shield member, whereby the position of the shield member can be adjusted from an inoperative position to at least one operative position, the shield member comprising a vanity mirror having a mirror member and a loudspeaker having a bending wave panel-form acoustic member, the mirror member and the panel-form member being integral. The shield member may define a hollow enclosure, in which one face of the panel-form member is enclosed to reduce or prevent sound radiation from that one face. The panel-form member may be a resonant member, e.g. according to WO97/09842 and U.S. counterpart application Ser. No. 08/707,012, filed Sep. 3, 1996. The sun visor may comprise an inertial electrodynamic vibration exciter on the panel-form member for applying bending wave vibration thereto.
The application of DM technology to the problem of providing a loudspeaker in an automobile sun visor, where the range of angles of adjustment of the visor causes large changes in response with conventional speakers, results in improved performance since a DM loudspeaker type has a highly consistent response over a range of angles.
The visor may be used for mobile telephony and/or for music reproduction, with distributed mode action and acoustic output resulting in superior clarity and intelligibility in this application. The panel-form device may also form or incorporate a microphone to enhance its application to mobile telephony.
From another aspect the invention is a vehicle rear view mirror comprising a body member and an adjustable support structure for the body member, whereby the position of the body member can be adjusted, the body member comprising a mirror member and a loudspeaker having a bending wave panel-form member, the mirror member and the panel-form member being integral. The body member may define a hollow enclosure, and one face of the panel-form member may be enclosed in the hollow enclosure to reduce or prevent sound radiation from that one face. The panel-form member may be a resonant member. The rear view mirror may comprise an inertial electrodynamic vibration exciter on the panel-form member for applying bending wave vibration thereto.